I haven't tested it, but this should be slightly simpler, and work better for subsequent review iterations (reviewing what changed once PR is updated):
jj new main -m review
jj new -m pr
jj git fetch
jj restore --from=big-change@origin .
Then keep squashing from `pr` to `review` as described in the article. When the PR gets a new version, rerun the last 2 commands.
This is very nice, I just tried it, thanks for the suggestion. I was messing around with rebasing subsequent PR updates onto the review commit but it got a bit messy with conflicts. The `jj restore` should solve it